A network consists of two or more computers that are linked in order to share resources (such as printers and scanners), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams

Goals of Networking – is to make resources shared by a remote system act as a resource on a local system

LAN-Local Area Network a group of computers connected within a buildingor a campus (Example of LAN may consist of computers located on a single floor or a building or it might link all the computers in a small company

WAN-A network consisting of computers of LAN's connected across a distance WAN can cover small to large distances, using different topologies such as telephone lines, fiber optic cabling, satellite transmissions and microwave transmissions.

MAN- A network of LAN's that covers a city or large campus environment

PAN- Personal Area Network (Individual Networks)

Other Type of Networks

WLAN - Wireless Local Area Network

SAN - Storage Area Network

CAN - Campus Area Network

GAN – Global Area Network

Workgroup vs. Domain

Workgroup model, every computer in the network has equal access to one another and is responsible and maintains its own set of users and passwords.

Domain model maintains a single database of user logins for the entire network

Network Interface Card - A network interface card (NIC) is a computer circuit board or network card that is installed in a computer so that it can be connected to a network.

NIC cards must implement a standard signaling methodology to gains access to a network.

Access Method: How a network device will communicate with one another CSMA/CD
CS (Carrier Sense) before transmitting, listen for signal; if none is found, it is the OK to transmit
MA (Multiple Access) all computers share the same media and signaling techniques.
CD (Collision Detection) Detect collisions, wait and retransmit

CSMA/CACS (Carrier Sense) Before transmitting, listen for signal; if none is found, it is the OK to transmit
MA (Multiple Access) All computers share the same media and signaling techniques.
CA (Collision Avoidance) Avoid collisions, wait and retransmit

Token Passing - Token is passed sequentially to each computer on the network based on a NIC's ID.

Baseband vs. Broadband

Baseband use time division multiplexing

Broadband use
frequency division multiplex

Full Duplex vs. Half Duplex communications

Unicast – One to one transmission

Multicast – One to some transmission

Broadcast – One to all transmission

A broadcast domain refers to a logical part of a network, in which any equipment within the network can directly send data to another equipment or device. When in the broadcast domain, data transfer can be done without going through a routing device.

Collision Domain – is a section of a network where packets can collide with one another when being send on a shared medium or through repeaters, in particular early version of Ethernet.

Public (Internet), Private (Intranet), Two different companies with secure connection (Extranet)

Static (IP is permanent) Dynamic (DHCP gives client IP address)

Packets vs. Frames

A frame is defined as the unit of data transferred across a network

Nic card sends data in discrete chunks called frames.

Preamble

MAC
Destination Address

MAC
Source
Address

Length

Data

Pad

CRC

Preamble – All Ethernet Frames begin with a Preamble 64bit series of 1’s and 0’s This is the start of a frame

MAC Address – Media Access Control a Unique ID of a NIC card (Recipient and Sender)

Length – An Ethernet Frame carry up to 1500 bytes of data in a single frame

Data – Information Data of what the frame carries

Pad – Will add extra data if not 64 bytes in size

CRC-Cyclic Redundancy Check is used for correction
within the frames are information called packets

A packet can be defined as the unit of data at any layer of the protocol stack, prior to, or after transmission Packets contains the following information